Packet data transmission in code-division multiple access communication systems

ABSTRACT

A system and method for the wireless transmission of data packets in a code division multiple access communication system wherein one of the code division multiple access channels (PRCH) is used in a time-shared fashion for the transmission of the data packets from several transmitting stations (MSy, MSz) to a receiving station (BS). 
     A request is sent from a transmitting station (MSy) to the corresponding receiving station (BS) of the communication system indicating the destination address to which data packet(s) are to be routed. 
     Then, registering the transmitting station (MSy) and assigning an unique virtual connection identifier (VCIy) to it. 
     Next, the transmitting station (MSy) is attached to the code division multiple access channel (PRCH) used for the transmission of data packets. 
     Then, listening to the downlink of the code division multiple access channel (PRCH) used for the transmission of data packets until the corresponding receiving station (BS) broadcasts that it will be “idle” such that a random access to the code division multiple access channel (PRCH) used for the transmission of data packets is allowed in the next frame. 
     Next, the transnmission power of the transmitting station (MSy) is ramped up during the next frame until a certain power level is reached. 
     The data packet(s) and the virtual connection identifier (VCIy) are transmitted over the uplink of the code division multiple access channel (PRCH) used for the transmission of data packets to the receiving station (BS). 
     The data packet(s) are routed to the destination address. 
     Access to the code division multiple access channel (PRCH) used for the transmission of data packets is controller by a multiple access protocol based on carrier sensing and collision detection (CSMA/CD).

TECHNICAL FIELD

The present invention concerns communication systems employingCode-Division Multiple Access (CDMA).

BACKGROUND OF THE INVENTION

Current digital cellular systems such as the Global System for MobileCommunication (GSM) or the Digital Cellular System 1800 (DCS-1800) inEurope, and the Personal Communication Networks (PCN) planned in theU.S. support mainly voice, message, and low-rate connection-orienteddata services which are not well suited to support packet-based datacommunication.

Many mobile computer applications, however, require infrequent transfersof single or multiple data packets over the radio link of the mobilecommunication system. Some of them, e.g., e-mail, tele-shopping andtele-banking, and vehicle-dispatch or fleet management applications maybe well served with a store-and-forward short message service. Others,among them terminal emulation, remote access to local area network (LAN)based servers, or credit-card verification require interactive usage,tolerate little delay, and are characterized by a wide distribution ofpacket length. There is little doubt that future mobiletelecommunication systems such as the Universal Mobile TelecommunicationSystem (UMTS) will have to support such data applications with anefficient packet-data service. In fact, the European TelecommunicationSystems Institute (ETSI) is already in the process of defining such aservice, called General Packet Radio Service (GPRS), as an extension tothe current GSM system.

In the sequel, we will consider connection-less packet-data services forUMTS and PCN systems. In particular, we focus on the UMTS system whichwas developed in a code division testbed (CODIT) project under theumbrella of the Research in Advanced Communications in Europe (RACE)program. The CODIT system employs spread-spectrum transmission and codedivision multiple access (CDMA) and supports voice, message, andconnection-oriented data services. For more details on the CODIT systemplease refer to “Design Study for a CDMA Based Third-Generation MobileRadio System”, A. Baier et al., IEEE J. Selected Areas Commun., Vol. 12,1994, pp. 733-743. CDMA systems are of particular interest because theypromise higher capacity and more ease of deployment than competingtime-division multiple access (TDMA) systems.

It is an object of the present invention to provide a method andapparatus which enables CDMA-based UMTS and PCN systems to support aconnectionless packet-radio service.

It is a further object of the present invention to provide acommunication system with added functionalities.

SUMMARY OF THE INVENTION

This has been achieved by the transmission of data packets over a codedivision multiple access wireless channel (PRCH), reserved for datapacket services, from a transmitting station (MSy) to a receivingstation (BS) of a code division multiple access communication system,comprising the following steps:

sending a request from said transmitting station (MSy) to thecorresponding base station (BS) of said communication system indicatingthe destination address to which said data packet(s) are to be routed,

registering said transmitting station (MSy) and assigning a uniquevirtual connection identifier (VCIy) to it,

switching said transmitting station (MSy) to said channel (PRCH),

listening to the downlink of said channel (PRCH) until said base station(BS) broadcasts that it will be “idle”, i.e. that a random access tosaid channel (PRCH) is allowed in the next frame,

ramping up the transmission power of said transmitting station (MSy)during said next frame until a certain power level is reached,

transmitting said data packet(s) and said virtual connection identifier(VCIy) over the uplink of said channel (PRCH) to said base station (BS),and

rerouting said data packet(s) to said destination address, the access tosaid channel (PRCH) being controlled by a multiple access protocol basedon carrier sensing and collision detection (CSMA/CD).

DESCRIPTION OF THE DRAWINGS

The invention is described in detail below with reference to thefollowing schematic drawings.

FIG. 1 shows a typical network as defined by CODIT.

FIG. 2A shows the mobile side of the CODIT protocol architecture,modified in accordance with the present invention.

FIG. 2B shows the network side of the CODIT protocol architecture,modified in accordance with the present invention.

FIG. 3A shows a flow diagram for the medium access control (MAC)protocol in a base station, according to the present invention.

FIG. 3B shows a flow diagram for the MAC protocol in a MS, according tothe present invention.

FIG. 4 is a timing diagram for the slotted carrier sense multiple accesscollision detection (CSMA/CD) protocol, according to the presentinvention.

FIG. 5 is a block diagram used to illustrate the transmission scheme ofthe present invention.

GENERAL DESCRIPTION

Details of the present invention will now be described by means ofreference to the enclosed Figures. An implementation of the invention isthen given as an example.

The present invention concerns a method and means for its implementationfor introducing a connection-less packet radio service intocode-division multiple access communication (CDMA) systems.

A typical CDMA network system is illustrated in FIG. 1. It comprisesfour different functional entities; the mobile stations (MS1-MS4)10.1-10.4, the base stations (BS1, BS2) 11.1 and 11.2, the radio networkcontroller (RNC) 12, and the mobile control node (MCN) 13. The RNC 12 isconnected via the MCN 13 to a fixed network 14 such as the Internet.This is the architecture we will adhere to when describing the presentinvention. As outlined in FIG. 1, several base stations communicate withone RNC through one interface. Similarly, a number of RNCs might beconnected to one MCN, which in turn connects to the fixed network 14. AMS can be connected to several base stations, i.e. when it is inmacro-diversity mode or performs a handover.

If a MS wants to communicate via a wireless network only infrequently,it makes little sense to occupy a connection to a BS, because the userwould not be willing to pay for such a connection. Furthermore, it isimportant to note that there is just a limited amount of channelsavailable within a cell. If all mobile stations within reach of the BSin this cell try to establish a permanent connection, the whole systemwould be blocked soon. The few permanent channels in such a cell shouldbe reserved for users transmitting and receiving voice and long dataframes.

According to the present invention, at least one of the CDMA channelsprovided by a BS in a cell is now time-shared between several infrequentusers, whereas all other channels remain reserved for other users.

In order to support a potentially sizable number of mobile stations,each exchanging packets with the fixed side of the network onlyinfrequently, and to make efficient use of already existing systemresources, a new logical channel, to be added to a CDMA-based UMTS orPCN system, such as the CODIT system described in “Design Study for aCDMA Based Third-Generation Mobile Radio System”, A. Baier et al., IEEEJ. Selected Areas Commun., Vol. 12, 1994, pp. 733-743, is hereindisclosed and claimed. This new logical channel is a packet radiochannel (PRCH) which is used by a single user or time-shared by severalusers.

According to the first embodiment of the present invention, access tothis PRCH is controlled by the basestation(s) and the radio networkcontroller (RNC). It is also conceivable to employ a separate PRCHcontroller, which interacts with the BSs and/or RNC.

In order to add as little complexity to the underlying UMTS or PCNsystem as possible, the physical layer supporting the PRCH is keptlargely unchanged. Preferably, a long spreading code is used for thephysical data channel (PDCH) and the physical control channel (PCCH),and coherent demodulation is employed for the uplink (UL), i.e. the linkbetween MS and BS, and downlink (DL) PDCH, i.e. the link between BS andMS. The PCCH might be coherently demodulated on the DL anddifferentially coherently demodulated on the UL. The interference due topacket transmission is similar to that from conventional speech and datachannels.

Because a connection built-up takes between 1 and 2 seconds in aconventional CDMA system, which is not acceptable in case of packet datatransmission, a different approach had to be sought.

According to the present invention, accelerated power control andchannel estimation are helpful to obtain acceptable throughputperformance in particular for short packets. In addition, the PRCHcoding and interleaving scheme should be carefully optimized to achievelow overhead and delay for short packets while guaranteeing acceptableerror protection for long packets.

An implementation of the present PRCH and its integration into theoverall system concept are now discussed.

The PRCH channel:

The inventive packet radio service is provided to all MSs within a cellof a network system via the PRCH, as shown in FIG. 1. Each BS 11.1, 11.2establishes and terminates one or multiple PRCHs on request of theRNC/MCN 12, 13. According to the first implementation, the PRCH is afull-duplex, asymmetrical channel that can be operated independently inboth directions at variable user data rates, e.g. for the present CODITsystem up to 9.6 kbps (narrowband channel) or up to 128 kbps (mediumbandchannel). The MCN 13 can attach multiple mobile users to a PRCH.Consequentially, mobile users have to register for this service at theMCN before they can get access to the channel. In order to distinguishbetween different users on the PRCH, the MCN assigns to each MS avirtual connection identifier (VCI) when it grants access. The VCI isrepresented with q bits and serves as a unique address within thelocation area, e.g. a micro cell, governed by the MCN. The number q hasto be chosen so that all MSs attached to the PRCHs can be addressedindividually. The PRCH is preferably structured in 10 ms time slots(frames) to convey fragmented packets between the MS and the network.

The MCN can send user data packets to one or several users on the DL andinformation for controlling the access and data transfer on the UL. Onthe UL, the MSs contend for access in short time periods when thechannel (PRCH) is indicated “idle”. After having gained access, therespective MS transfers the packets to the network. The logical channelPRCH is mapped onto a single physical channel comprising the physicaldata channel (PDCH) and the physical control channel (PCCH); therefore,only a single basestation transceiver is required for supporting onePRCH. This means that a base station supporting 10 CDMA channels having10 transceivers now provides 9 CDMA channels and 1 PRCH, according tothe present invention. I.e., one of the transceivers is employed tosupport the packet data service.

FIGS. 2A and 2B illustrate how the PRCH is incorporated into the C-planeof the CODIT protocol architecture. The structure depicted in FIGS. 2Aand 2B is layered in accordance with the open systems interconnection(OSI) reference model as described in the article “Radio ProtocolArchitecture of the CODIT UMTS System: E. Berruto et al., Proceedings of1994 International Zurich Seminar on Digital Communications, March 1994,Springer, Lecture Notes in Computer Science. The architecture is splitinto a physical layer (layer 1) 20, a data link layer (layer 2), and anetwork layer (layer 3) 24. The data link layer is further split intothree parts, namely, data link control (DLC) 23, and two medium accesscontrol (MAC) parts 21 and 22. The DLC layer 23 is concerned with linkestablishment, release and maintenance. The lower MAC part 21, depictedas MAC*, may exist in multiple instances, whereas the upper MAC part 22(MAC**) is unique. Physically, the two MAC parts 21 and 22 are separatedon the network side because the MAC** part resides in a RNC while thelower part MAC* exists in each base station, as indicated in theannotations on the right hand side of FIG. 2B.

The connectionless packet service (CLPS) entity 25.1 of layer 3, i.e.the network layer 24, provides the packet radio service to the mobileuser, see FIG. 2A, and the CLPS entity 25.2 on the network side providesall facilities required for registration and authentication of mobileusers, see FIG. 2B, assigning and administrating their VCIs, andinterfacing to a packet data network. The CLPS entities 25.1 and 25.2use the logical link administrators (LLA) 26.x to initially routemessages via a regular dedicated control channel (DCCH) 27.x to theirpeer entities. After the MS is attached to the PRCH, all messagesexchanged between the CLPS entities 25.× as well as user data packetsare always directed via the respective PRCH 28.x. In this case, thecontrol packets and user data packets are passed through the DLC 29.x tothe packet radio (PR) control entity 30.x The packets are fragmented andprotected with an error control code, e.g. a block code (BC), by arespective unit 31.x for detecting transmission errors on the receivingside. Then they are convolutionally encoded, interleaved (IL) by theentity 32.x, and then transmitted over the PDCH 33. Some controlinformation, e.g. for power control, may also be transferred via thePCCH 34. On the receiving side, see FIG. 2B, the fragments are thenreconstructed from the received samples, reassembled to packets, andforwarded to the target CLPS entity 25.2. When the decoder, e.g. a blockdecoder 31.2 in case of block coded packet transmission, detects thereceipt of an erroneous packet fragment, an automatic request forrepetition (ARQ) scheme provided in the PR control requests itsretransmission.

In the next section it is described how a mobile user can initially beattached to the packet data channel or detached from it.

PRCH attach/detach procedure:

It is assumed that the MS is in the state “broadcast active”, that is,the MS receiver has already acquired chip and frame synchronization andlistens to the broadcast channel (BCH). Now the following actions areperformed in accordance with the present invention:

1. When a mobile user requests the MS to attach its transceiver to thePRCH it performs a regular random access to establish a DCCH 27.1 forexchanging signaling messages only. During this procedure, the MSoperates in the state called “random access”. This random access isdescribed in the above mentioned article of A. Baler et al.

2. After the DCCH 27.1 is established, the MS is in the state“connection established”. The MS can now send the messagePRCH_ATTACH_REQ to the MCN indicating the destination address for allpackets to be sent.

3. On receipt of the PRCH_ATTACH_REQ, the MCN checks the traffic load onthe PRCHs and performs authentication in the location area, registersthe MS together with the corresponding destination address, and assignsa VCI to the MS. The MCN allows the MS to access the PRCH 28.1 bysending the message PRCH_ACCESS_GRANT with the parameters VCI and thephase and frame offset between the DCCH 27.1 and assigned PRCH 28.1.

4. When the MS receives PRCH_ACCESS_GRANT, the MS switches itstransceiver to the PRCH 28.1 and starts operating in the state “attachedto PRCH”. In this state, the MS receiver listens to the downlink inorder to receive data packets carrying its VCI and control informationfor the uplink PRCH. If the BS indicates that the uplink PRCH is idle,the MS transmitter may initialize a data packet transfer to the networkside as will be described later.

5. When the MS or the RNC intends to detach the MS from the PRCH, amessage PRCH_DETACH_REQ is exchanged via the PRCH which switches the MSback to the state “broadcast active”.

The following section deals with the data packet transfer via the PRCH.

Data transfer over the PRCH channel:

As other channels in the present CDMA system, the PRCH is mapped onto aPDCH 33 and a PCCH 34 both preferably having a 10 ms frame structureaccording to the present embodiment. On the PCCH 34, however, a 5 mssubframe structure is superimposed to allow the exchange of accesscontrol information in 5 ms time intervals between the MSs and the BS.In order to achieve short delays for the transmission of short packets,a coding scheme is proposed for the PRCH which consists of an innerconvolutional code in conjunction with an outer cyclic redundancy check(CRC) code. Whenever decoding of the outer code on the receiver sideindicates an error for a fragmented packet, a retransmission isrequested. Access to the PRCH is controlled by a multiple accessprotocol based on carrier sensing and collision detection (CSMA/CD),possibly coupled with a reservation method and provisions for supportingtime-critical applications with bounded delay requirements. In thefollowing, mainly the CSMA/CD part of the protocol will be described.Such a CSMA/CD protocol is usually employed in systems where thetransmitters can quickly detect idle and collision periods of multipleaccess channels. CSMA/CD is widely used in local area networks, such asfor example the Ethernet (IEEE 802.3 standard). According to the presentinvention, the carrier sensing and collision detection is provided bythe BS, as will be described later in a section headed “CSMA/CD mediumaccess control protocol”.

Downlink (DL):

Fragmented user data packets, which have to be conveyed from the RNC toa registered MS via the PRCH, are transmitted on the DL PDCH over theradio link. Control information, which is required to support channelaccess control and data transfer on the UL, is transmitted from thenetwork side to the MSs either via the DL PDCH or the DL PCCH. On the DLPDCH, for example, retransmission requests of erroneously receivedpacket fragments on the UL are transmitted to the originating MS; ofcourse, these requests can be piggybacked on user data frames. On the DLPCCH, it is advantageous to indicate to all attached MSs, firstly, thedata rate presently used on the DL PDCH and, secondly, the data rate tobe used on the UL PDCH in the next 10 ms frame or frames. Moreover, abusy/idle flag is broadcasted to all attached MSs indicating whether arandom access is allowed in the next frame. All control information isprotected to guarantee reliable delivery to the MSs. Finally, someunprotected power control bits are also transmitted on the DL PCCH.

Uplink (UL):

First the case is considered where only one registered MS currently hasa packet to transmit.

1. The PR control entity 30.1 in the MS senses the DL PRCH. When thebusy/idle flag received via this DL PCCH indicates FOUL idle in the nextframe”, the PR control 30.1 triggers its transceiver to perform on theUL PCCH a so-called power ramping procedure starting in the next 10 mstime interval.

2. During power ramping, the MS transmits on the UL PCCH a preamble andincreases stepwise the transmit power. The MS receiver simultaneouslylistens to the power control information received on the DL PCCH. If thetarget power level is reached, the MS stops power ramping and startstracking.

3. During the reception of the preamble, the BS acquires chipsynchronization and estimates the channel. Simultaneously, the BS alwaysbroadcasts on the DL PCCH “UL busy in the next frame” to avoid thatother MSs start the random access procedure in the next frame.

4. After the power ramping phase, the MS transmits its first encodedpacket fragment on the UL PDCH and its VCI in the first UL PCCH 5 mssubframe. If further fragments have to be sent to convey the packet overthe radio link, the MS raises a more-frames flag which is alsotransmitted via the UL PCCH.

5. When the BS detects the VCI, it immediately acknowledges the VCI onthe second 5 ms subframe on the DL PCCH. Without getting theacknowledgment, the MS stops transmitting fragments immediately.

6. When the BS receives the first encoded packet fragment and the raisedmore-frames flag, the BS indicates on the DL PCCH “UL busy in the nextframe”. The packet fragment is decoded and checked for errors by units32.2 and 31.2 and then passed to the PR control 30.2.

7. The MS transmits the next encoded packet fragments on the UL PDCH.When the last frame is transmitted, the more-frames flag is switched offin the first subframe on the UL PCCH.

8. The BS decodes the received packet fragments and passes them to thePR control 30.2. As soon as the BS detects the last frame, it broadcasts“UL idle in the next frame” in the second subframe on the DL PCCH toagain allow a random access.

Optionally, the MS can transmit over the UL PCCH together with the VCIimmediately after power ramping the number of packet fragments to beconveyed over the radio link. After successful reception of these twoparameters, the BS indicates on the DL PCCH “UL busy in the next frame”until the number of correctly received fragments equals the announcednumber. When this option is implemented, there is no need to transmit amore-frames flag over the UL PCCH. It is now considered that there arepresently two or more MSs having packets to be transmitted.

All contending MSs perform power ramping as described in phases 1.) and2.) above, except that the BS limits the total power of all contendingMSs to the target power. In phase 3.), the BS regularly starts receptionand avoids new contenders. Then, the contending MSs start transmissionas described in phase 4.). If the BS can detect no VCI in phase 5.), itacknowledges none of the contending MSs which forces them to ceasetransmission immediately and to try to access the PRCH individually sometime later to retransmit the whole packet. Additionally, the BSbroadcasts on the DL PCCH “UL idle in the next frame” to again allowrandom access. If the BS can detect the VCI of a MS, however, itacknowledges this (strong) MS which leads the other contenders to ceasetransmission immediately and to try to access the PRCH individually sometime later to retransmit the whole packet. The acknowledged MS and theBS then proceed as it is described in phases 6.) to 8.) above.

Finally, it is considered that none of the registered MSs presently hasa packet to transmit.

If the BS fails to detect some signal energy on the PCCH in phase 3.),it broadcasts on the DL PCCH “UL idle in the next frame” in thefollowing frame.

CSMA/CD medium access control protocol: Since the present system isbased on a 10 ms frame structure, the use of a slotted MAC protocol with10 ms PRCH frames corresponding to slots has been adopted. In contrastto the 10 ms frame structure on the PDCH, the PCCH channel employs a 5ms subframe structure.

In FIGS. 3A and 3B, the flow diagrams of the UL MAC protocol in the BSand MS are shown, respectively. It is assumed that the time unitcorresponds to a 10 ms frame and k denotes the current frame number. TheBS indicates on the DL PCCH channel the transmission rate R required onthe UL in the next frame. The variable rate R might for example beselected from a predetermined set of transmission rates such that thetotal interference does not exceed a precomputed threshold.

R=0 implies that the UL will be idle during the next frame. Only afterdetecting R=0, called carrier sensing, the MSs attached to the PRCHchannel may access the UL in the following frame, provided that theyhave a packet to (re)transmit. According to this scheme, on the UL PCCHchannel, the MSs transmit a preamble with an initial power being about10 to 20 dB below the target power, e.g. indicated by an open loop powercontrol as described in the above mentioned article of A. Baier at al.During the power ramping phase (10 ms), the transmit power of the MS isadjusted according to the power control commands on the DL PCCH channel,which might operate at 2 kbit/s, such that the sum of the total powerreceived from all MSs currently accessing the channel is as close aspossible to the target power of the closed loop power control.

The BS indicates that the UL PRCH is “busy” (R>0) or “idle” (R=0) in thefollowing frame depending on whether the total detected signal energyexceeds a predetermined threshold. If R=0, the MSs retransmit thepreamble in the next frame in order to access the channel. If R>0,however, the MSs transmit the first 10 ms data frame on the UL PDCH 10channel at data rate R and the encoded virtual connection identifier(VCI) as well as the more indicator M on the UL PCCH channel. M=1informs the BS that there are more frames to be transmitted whereas M=0means that there are no more frames to come. Assuming that the BSsucceeds in decoding a single VCI and M=1, it indicates the required ULtransmission rate R>0 for the next frame on the DL PCCH. If the BS failsto decode a VCI or detects M=0, it indicates R=0 “idle” for the nextframe. Once a MS detects R>0, it continues transmitting data on the ULPDCH if it has another frame to send (M=1).

On the other hand, a MS stops transmitting data after the detection ofR=0, because it either experienced a collision—the first frame of thepacket is lost and the packet must be retransmitted—or because it sent apacket consisting of one frame only.

The timing diagram in FIG. 4 illustrates the “success”, “collision” and“idle” periods on the UL PRCH channel. After detecting the last frameindicator M=0 of MSx during the first 10 ms frame k=1, the BS indicateswith R=0 in the second half 41 of the first frame of the DL PCCH channelthat the second frame k=2 on the UL will be idle. Since only MSy in theexample depicted in FIG. 4 has a packet to transmit, it starts powerramping (hatched triangle 46) during the second frame k=2 on the UL PCCHchannel. After the BS has detected some signal energy within the first 5ms 42 of the second frame, it informs all the MSs that the UL will bebusy during the third frame k=3 by indicating the UL transmission ratefor the next frame R=R₁ on the DL PCCH channel. During the third frame,MSy transmits data at rate R₁ on the UL PCCH channel and both the VCIyand M=1 on the UL PCCH channel. The BS decodes the VCIy of MSy andinforms again all the MSs that the UL is busy during the fourth framek=4 by indicating R=R₁ on the DL PCCH channel. Since the packet 43 (datay) of MSy is only two frames long, MSy informs the BS with M=0 in thefirst half 44 of the fourth frame k=4 that the last data frame is beingtransmitted. After detecting R=0 at the end of the fourth frame, MSx andMSz now attempt to access the UL channel via power ramping(cross-hatched triangle 45) during the fifth frame k=5. Since the BScannot detect a VCI in the sixth frame, it indicates with R=0 that theUL will be idle during the following frame. MSx and MSz detect thecollision and in turn stop transmitting data at the end of the sixthframe k=6. The BS cannot detect sufficient signal energy in the seventhframe k=7 either and the UL remains idle (R=0) during the followingframe.

A possible implementation of a part of a transmitter 50, including thepresent invention, is shown in FIG. 5. This transmitter is based on theone described in an article called “A CDMA-Based Radio Access Design forUMTS”, P.-G. Andermo et al., IEEE Personal Communications, February1995, pp. 48-53. Positioned on top is a configuration unit 51. It playsa vital role, since after having received the applicable informationabout carrier frequency, chip rate and service identifier from theresource manager, it can control how information is coded, multiplexedand converted to RF. When a connection is established, the radioresource manager, which is located in the network, determines theseparameters based on the requested service by the user, service beingoffered in the particular area, and the actual system load. Asillustrated in FIG. 5, information to be transmitted enters from theleft hand side on different logical channels. These logical channels maycarry speech, user data and control information. The latter is denotedthe dedicated control channel (DCCH) 52, and carries, for example,measurement reports, handover commands, etc., while the former two andthe inventive packet channel 53 fall into the category of trafficchannels, denoted TCH/S, TCH/D, and PRCH, respectively. The inventivepacket service is achieved by providing a block encoder 31.2, followedby a convolutional encoder and interleaver 32.2, as illustrated in FIGS.2A, 2B and 5.

According to another embodiment of the present invention the user datarates on the packet data channel may be allocated in a dynamic fashion,e.g. depending on the current traffic load on this channel.

The present packet data transmission scheme provides for high packetthroughput with an emphasis on packets of short length. However, it isequally suited for other messaging and packet applications such ase-mail, tele-shopping and tele-banking, and vehicle-dispatch or fleetmanagement applications, for example.

What is claimed is:
 1. Method for the wireless transmission of datapackets in a code division multiple access communication system whereinone of the code division multiple access channels (PRCH) is used in atime-shared fashion for the transmission of the data packets fromseveral transmitting stations (MSy, MSz) to a receiving station (BS),comprising the following steps: sending a request from a transmittingstation (MSy) to the corresponding receiving station (BS) of saidcommunication system indicating the destination address to which saiddata packet(s) are to be routed, registering said transmitting station(MSy) and assigning an unique virtual connection identifier (VCIy) toit, attaching said transmitting station (MSy) to said code divisionmultiple access channel (PRCH) used for the transmission of datapackets, listening to the downlink of said code division multiple accesschannel (PRCH) used for the transmission of data packets until thecorresponding receiving station (BS) broadcasts that it will be “idle”such that a random access to said code division multiple access channel(PRCH) used for the transmission of data packets is allowed in the nextframe, ramping up the transmission power of said transmitting station(MSy) during said next frame until a certain power level is reached,transmitting said data packet(s) and said virtual connection identifier(VCIy) over the uplink of said code division multiple access channel(PRCH) used for the transmission of data packets to said receivingstation (BS), and routing said data packet(s) to said destinationaddress, the access to said code division multiple access channel (PRCH)used for the transmission of data packets being controlled by a multipleaccess protocol based on carrier sensing and collision detection(CSMA/CD).
 2. The method of claim 1, wherein said communication systemoffers a connectionless packet data services.
 3. The method of claim 1,wherein at least two transmitting stations (MSx, MSz) intend to transmitdata packet(s) and independently perform said power ramping and whereinsaid receiving station (BS) limits the total power of all contendingtransmitting stations (MSx, MSz) to a target power.
 4. The method ofclaim 1, wherein said receiving station (BS) indicates to saidtransmitting station (MSy) the data rate to be used on the uplink ofsaid code division multiple access channel (PRCH) used for thetransmission of data packets during the next frame or frames.
 5. Themethod of claim 1, wherein power control information is fed back fromsaid receiving station (BS) to said transmitting station (MSy) duringthe power ramping step.
 6. The method of claim 1, wherein a transmittingstation (MS) is registered only if traffic load on the network permits.7. The method of claim 1, wherein a long spreading code is used totransmit the data packet(s).
 8. The method of claim 7, wherein an innerconvolutional code in conjunction with an outer cyclic redundancy check(CRC) code is used.
 9. The method of claim 1, wherein coherentdemodulation is employed on the uplink and downlink of said codedivision multiple access channel (PRCH) used for the transmission ofdata packets.
 10. The method of claim 9, wherein the physical controlchannel (PCCH) of said code division multiple access channel (PRCH) usedfor the transmission of data packets is coherently demodulated on thedownlink and differentially coherently demodulated on the uplink. 11.The method of claim 1, wherein said code division multiple accesschannel (PRCH) used for the transmission of data packets is afull-duplex, asymmetrical channel that can be operated independently inboth directions at variable user data rates up to 9.6 kbps (narrowbandchannel) or up to 64 kbps (mediumband channel).
 12. The method of claim1, wherein said code division multiple access channel (PRCH) used forthe transmission of data packets is structured in 10 ms time frames. 13.The method of claim 1, wherein said data packet services are used forexchanging E-mail type of packets.
 14. The method of claim 1 or 3,wherein said receiving station (BS) acknowledges none of the contendingtransmitting stations (MSx, MSz) if it is not able to detect any oftheir virtual connection identifiers (VCIx, VCIz).
 15. The method ofclaim 14, wherein said contending transmitting stations (MSx, MSz) ceasetransmission immediately if they do not receive said acknowledgementfrom said receiving station (BS) and try to access said code divisionmultiple access channel (PRCH) used for the transmission of data packetslater to retransmit the whole data packet(s).
 16. The method of claim 1,wherein long data packets are fragmented so as to fit into the frames ofsaid code division multiple access channel (PRCH) used for thetransmission of data packets.
 17. The method of claim 1, wherein datarates on said code division multiple access channel (PRCH) used for thetransmission of data packets can be allocated in a dynamic fashion, e.g.depending on the current traffic load on this code division multipleaccess channel (PRCH) used for the transmission of data packets. 18.Code division multiple access communication system for the wirelesstransmission of data packets wherein one of the code division multipleaccess channels (PRCH) is used in a time-shared fashion for thetransmission of the data packets from several transmitting stations(MSy, MSz) to a receiving station (BS), comprising: means for sending arequest from a transmitting station (MSy) to the corresponding receivingstation (BS) of said communication system indicating the destinationaddress to which said data packet(s) are to be routed, means forregistering said transmitting station (MSy) and assigning an uniquevirtual connection identifier (VCIy) to it, means for attaching saidtransmitting station (MSy) to said code division multiple access channel(PRCH) used for the transmission of data packets, means for listening tothe downlink of said code division multiple access channel (PRCH) usedfor the transmission of data packets until said receiving station (BS)broadcasts that it will be “idle” such that a random access to said codedivision multiple access channel (PRCH) used for the transmission ofdata packets is allowed in the next frame, means for ramping up thetransmission power of said transmitting station (MSy) during said nextframe until a certain power level is reached, means for transmittingsaid data packet(s) and said virtual connection identifier (VCIy) overthe uplink of said code division multiple access channel (PRCH) used forthe transmission of data packets to said receiving station (BS), andmeans for routing said data packet(s) to said destination address, meansfor controlling the access to said code division multiple access channel(PRCH) used for the transmission of data packets by a multiple accessprotocol based on carrier sensing and collision detection (CSMA/CD). 19.Transceiver for use in a code division multiple access communicationsystem for the wireless transmission of data packets, wherein one of thecode division multiple access channels (PRCH) is used in a time-sharedmanner for the transmission of the data packets from several stations(MSy, MSz) to a receiving station (BS), comprising: means for sending atransmission request from a station (MSy) to the corresponding receivingstation (BS) of said communication system indicating the destinationaddress to which said data packet(s) are to be routed, means forattaching said station (MSy) to said code division multiple accesschannel (PRCH) used for the transmission of data packets, means forlistening to the downlink of said channel (PRCH) until said receivingstation (BS) broadcasts that it will be “idle” such that a random accessto said code division multiple access channel (PRCH) used for thetransmission of data packets is allowed in the next frame, means forramping up the transmission power of said station (MSy) during said nextframe until a certain power level is reached, and means for transmittingsaid data packet(s) and said virtual connection identifier (VCIy) overthe uplink of said code division multiple access channel (PRCH) used forthe transmission of data packets to said receiving station (BS).
 20. Thesystem of claim 18, wherein said receiving station (BS) comprises meansto indicate to said transmitting station (MSy) the data rate to be usedon the uplink of said code division multiple access channel (PRCH) usedfor the transmission of data packets during the next frame or frames.21. The transceiver of claim 19, wherein said transmitting station (MSy)comprises means to adjust the data rate to be used on the uplink of saidcode division multiple access channel (PRCH) used for the transmissionof data packets as indicated by a receiving station (BS).
 22. The systemof claim 18 or the transceiver of claim 19, comprising means forencoding data packet(s) to be transmitted by a long spreading code. 23.The system of claim 18, wherein said code division multiple accesschannel (PRCH) used for the transmission of data packets is afull-duplex, asymmetrical channel that can be operated independently inboth directions at variable user data rates up to 9.6 kbps (narrowbandchannel) or up to 64 kbps (mediumband channel).
 24. The system of claim18, wherein said code division multiple access channel (PRCH) used forthe transmission of data packets is structured in 10 #ms time frames.25. The transceiver of claim 19, comprising means to fragment long datapackets so as to fit them into the frames of said code division multipleaccess channel (PRCH) used for the transmission of data packets.